The AHK source (DimScreen.ahk) is available, but unfortunately, there is no AHK for Linux, as far as I know, or at least nothing that can run an AHK script. It's kind of a Windows only thing.

Although in some cases, with limited success, a compiled AHK script (.exe) can be run with WINE. It really depends on what it does. I don't think in this case that it would work out very well (although I could be wrong).